February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index

Excerpt from A Recording Soil Moisture Tensiometer The simple - design recorder can be built with readily available materials in a shop equipped with wood and metal working equipment by anyone familiar with these tools. It is composed of four basic sys tems: (l) the porous cup and re lated tubing; (2) the manometer, scale, and mercury storage cup; (3) the float-and-lever system and pen; and (4) the chart drum and drive. These systems are mounted on a plywood and plastic base. The porous cup (fig. 2) is placed in the soil at the desired depth, and the transfer of water through the cup changes the water volume in the manometer system. Two small nylon tubes extend to the soil surface and connect the porous cup to a flushing tube and the recorder. The connecting tubing is cut to lengths suitable to the particular installation. The flushing tube is used primarily to fill the porous cup and balance the manometer system. The recorder tube is sealed to the top of the glass manometer at the recorder. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.